<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <button onclick="fn(this)">1</button>
    <button>2</button>
</body>
<script>
    function fn(_this){
        console.log(_this)
    }
    // const btns = document.querySelectorAll("button");
    // btns[1].onclick = () => {
    //     console.log(this);
    // }
</script>
</html>